Study On The Mechanisms Of Sucrose-metabolizing During The Development Of Longan Fruit

‘Fuyan’longan (Dimocarpus longan Lour.) which planted in East of Fujian province and‘Fuyan’,‘Dongbi’,‘Wolongling’in South of Fujian were used as experimental material, The component and content of sugar, changes of activies of sucrose-metabolizing related enzymes and photosynthesis characteristics of leaves pericarp were studied during the development of fruit, the main results were as follows:1.The longitudinal and horizontal diameter of longan fruit increased gradually aftert 30 days of full bloom, and the young fruit of‘Dongbi’was the biggest of all, but it became the smallest when ripped, the fruit of‘Wolongling’was the biggest when it ripped. The size of‘Fuyan’fruit in two areas was identical. The content of glucose, sucrose and fructose in fruit of longan accumulated in‘S’curve from 30 days of full bloom. The dry weight of‘Dongbi’longan aril was more than that of‘Fuyan’and‘Wulongling’, dry weight of‘Fuyan’in South of Fujian was lower than that in East of Fujian when fruit was ripped.2.There were chlorophyll and carotenoids in pericarp of young longan fruit, which reached their minimum value at maturity. The main accumulation of soluble sugar in pericarp of longan was sucrose, glucose was the second; The chlorophyll content of pericarp had a correlation with sugar(sucrose, glucose and fructose.3.The starch content of longan aril decreased from the 40 days of full bloom to the maturity. The starch content of‘Fuyan’in East and South Fujian was significantly higher than that of‘Dongbi’, which showed that‘Dongbi’changed more completely in the hydrolysis of starch to sugar than‘Fuyan’, thus caused the content of soluble sugar was hogher. The starch content of‘Fuyan’in South of Fujian was higher than that of Ningde area when fruit was ripped.4.Sucrose, fructose and glucose were the main longan sugar during the development of the fruit’, and the content of sucrose was the highest of the three, the glucose was the next , and the fructose was the least of all. But the different varieties at different developmental stages had a big difference in this three kinds of sugars.5. Theα-amylase and amylase activity of longan aril accumulated in‘W’curve, the amylase total activity of‘Fuyan’in South of Fujian was higher than that in Ningde area. The aril starch content of‘Fuyan’and‘Wulongling’had a negative significant or very significant correlation with sucrose phosphatesynthase activity, and the starch content of Ningde‘Fuyan’also had a positively significant correlation withα-amylase activity, while the starch content of‘Dongbi’had a negative significant correlation with amylase activity. The Conversion of the sugar contents of‘Fuyan’had a correlation with neutral invertase, but it had an unremarkable correlation with acid invertase in fruit. Sucrose synthase activity were began to accumulate in‘S’curve during the whole development of longan fruit, sucrose synthase activity had an unremarkable correlation with the content of Soluble sugar. Sucrose phosphatesynthase activity gradually increased with the maturity of longan fruit. The content of glucose, sucrose and fructose of varieties longan aril had a positively significant or very significant correlation with sucrose phosphatesynthase activity, while the content of starch had a negative positively significant or very significant correlation with sucrose phosphatesynthase activity.6.The daily variation of longan leaves presented single-peak curve, and the highest peak value appeared at 12:40, there was different chlorophyll content in leaves of‘Fuyan’and‘Wulongling’, but Chl a/b value had no significant difference. There was insignificant difference in longn cultivars and chlorophyll fluocreacence parameters. No obvious difference was found in the net photosynthetic rate and transpiration rate when fruit was mature period, and the stomatal conductance of‘Fuyan’was significantly lower than‘Wulongling’. The transpiration rate in maturity was higher than florescence.